I know how to card duplicate, and it is 100% working, this technique can full the card slot of a gacha using only 1 card and making the card remain unused. this trick doen't consume socket jewel and etc.,
but the thing is i don't want to share it because i don't want it to be patch.
I will only share a clue, the clue is "MAKE YOUR PC LAG" then after that discover it by your self.
here an example:
PS: If you discover now this technique, it will help you to do an skill key duplicating also